HA16114P/PJ/FP/FPJ, HA16120FP/FPJ
7.2 Intermittent Mode Timing Diagram (V
only)
ON/OFF
*1
3VBE
c
c
2VBE
VON/
On
On
Off
VBE
0 V
IC is on
a
IC is off
b
t
TON
2TON
a. Continuous overcurrent is detected
TOFF
b. Intermittent operation starts (IC is off)
c. Voltage if overcurrent ends (thick dotted line)
Note: 1. VBE is the base-emitter voltage of internal transistors, and is approximately 0.7 V.
(See the figure 6.1.)
For details, see the overall waveform timing diagram.
Figure 7.2 Intermittent Mode Timing Diagram (V
only)
ON/OFF
7.3 Calculation of Intermittent Mode Timing
Intermittent mode timing is calculated as follows.
(1) TON (time until the IC shuts off when continuous overcurrent occurs)
1
2VBE
VBE
T
ON = CON/
= CON/
≈ 0.69 × CON/
× RB × ln
×
1 − On duty*
1
× RB × ln2 ×
× RB
1 − On duty*
1
1 − On duty*
×
(2) TOFF (time from when the IC shuts off until it next turns on)
V
IN − VBE
TOFF = CON/
× (RA + RB) × ln
VIN − 2VBE
Where VBE ≈ 0.7 V
The greater the overload, the sooner the pulse-by-pulse current limiter operates, the smaller tON becomes,
and from the first equation (1) above, the smaller TON becomes. From the second equation (2), TOFF depends
on VIN. Note that with the connections shown in the diagram, when VIN is switched on the IC does not turn
on until TOFF has elapsed.
Dead-band voltage
Sawtooth wave
Point at which the current
limiter operates
PWM output
(In case of HA16114)
tON
On duty =
× 100 (%)
tON
T
Where T = t/fOSC
T
Note: On duty is the percent of time the IC output is on during one PWM cycle
when the pulse-by-pulse current limiter is operating.
Figure 7.3
Rev.2.0, Sep.18.2003, page 17 of 37
RENESAS [ RENESAS TECHNOLOGY CORP ]
